Its true you cannot compare the two places. Alanya is nice but much more busy I found. The beaches are very nice and sandy though be careful of the waves. There are some flat rocks under the surf and I slipped a few times. Our hotel was really nice, a bit of a walk into town along the prom but really nice watching the sun go down. Harbour area I would compare to Marmaris, there are loads of eating places and full on bars & nightclubs.
Have fun!